This is probably old news to all on this forum, but I've noted that you only seem to level up when skills rank up. I've read briefly how this works and you can get to level 81 eventually. This would be with all skills maxed, correct?
I can't decide if this is a good thing or a bad thing. I only want my character to behave/fight in a certain way. Therefore, once all those relative skills are at 100, I will no longer continue to level up, even if I'm not at the soft cap of 50. Do you have to be a jack-of-ALL-trades to reach max level?

I think you'll be around level 50 with 6 skills max? I don't know the exact math. 50 is really as high as you need to get. Going any higher will probably bite you in the rear if/when we see monsters above level 50 other than Alduin.

There is no Soft Cap at 50. 50 is just the level at which most characters are so god like, that any more leveling is just academic. Plus, the game is not really designed to accommodate a character over level 50, as in challenges to that character or tasks suited to that character. It does not mean you can't continue to play, and it does not mean you will stop having fun. It just means that the challenges are over and what you encounter will be easy to deal with.

You keep getting perks and you keep leveling up as you use skills that are not at 100.

There's a soft cap at 50. You stop seeing enemies scale with your level, you mostly stop seeing new tiers of items (because there are no more, it doesn't go beyond daedric), your main combat skills are probably already capped so you'll only really indirectly get more powerful with a wider toolbox or possibly pick up some perks you skipped out on. Beyond level 50, all you are doing is making your character more homogenous and like any other character. It is definitely best to say "Yeah, I'm as high as I'll go" when you hit 50. I "grinded" Alteration (0 mana telekinesis + watch TV) and sort of regret it. You end up making your character something that it isn't just to raise some number and get some perks that probably won't offset the level advantage enemies get over you especially if you never use that skill often.

I think that only holds true if you play a very limited playstyle. If you actually like having options, there is quite a bit of utility being able to level past 50. For my own situation, now that my favored combat, armor, and crafting skills are either topped out or close to it, I'll start building my destruction magic to broaden my options in combat. You should never feel like you have to make a new character to enjoy different aspects of gameplay.

Bear in mind -- if you sell stuff, you're leveling Speech. If you're opening locks, you're leveling Lockpicking. If you get hit while wearing light or heavy armor, you're leveling the corresponding skill. If you heal yourself after combat, you're leveling Restoration. They may be small amounts if you're not focusing on those activities, but they add up over dozens of hours.

We haven't been hearing of people who stop being able to level before 50 because their playstyle uses only skills that have already hit 100.

Homogenous. What you said in your post, you are going to end up making your character a generic spellsword. This will likely kill your urge to play the game again because you feel like you've already done it, even though playing as a wizard is dramatically different from just turning a warrior into a spellsword at the end-game. I know. I played a warrior who became a spellsword, and spamming 0 mana cost spells and powerleveling your magic schools =/= actually playing the game as a wizard while leveling. It is actually fairly fun and it doesn't just feel like grinding.

Also, you don't really need those options. Once you're level 50, that's pretty much the end of the road. There aren't any big bads left to fight. Sure, you can do it to make your character feel "complete", but it really isn't needed in the slightest. If anything, it is going to hurt you if/when the level cap is raised.

You still wouldn't have enough perks to make EVERY SINGLE SKILL TREE viable, though.

Honestly, the perk system actually adds replay value to the game. Even if they weren't leveling you up in previous games, when you got to skill level 100 in your miscellaneous skills, you were just as good as someone who took the skill as a Major skill.

Well I'm level 44 and I feel like my character, while not invincible, doesn't "need" anymore levels in order to not really worry about dying, ever. Unless I fall asleep at the controller, which has happened.

Yet my lockpicking, light armor, one-handed, and many other skills are 50 or lower.

Yeah I personally use a Linear Leveling setup with this mod -- http://skyrimnexus.com/downloads/file.php?id=1992 , and use the improved maximum scaling of this mod -- http://skyrimnexus.com/downloads/file.php?id=1269 (also a lot of other changes that really help balance NPCs)

Problem is with maximum scaling, NPCs max out their intended skills relatively early, so you're not going to feel as threatened at Level 70 as Level 50 when that Bandit comes at you with increased health and 100 Smithing! Since they can't Smith their gear to be any better =/

And of course mods are only for PC.