I'll add my two pence...
I've played Football Manager (and CM before it became FM) since CM93/94 and I've played every single version. I absolutely love the game, and can spend periods of weeks/months hopelessly addicted to the game.
FM2008 is the best version so far,
IMO. There's a few problems I have with it, some irritating, some not so irritating:
1.) The media. The idea of media interaction is fantastic, but it's far too repetitive. As others have said it gets boring commenting on a player you're going to face who you sold several years ago, especially after commenting on the same player several times before. The media interaction needs an overhaul, and things like having a rant against your opponent should have more of an impact upon the players. Plus I'd like to see more player mind games prior to big games, like you get in Champions League games in real life. It'd be nice to have, for example, the ability to ask one of your players to slag off the opposition for being boring.
2.) Team talks. Good idea in principle, but I'm no fan of them. I'm not a master tactician and as such I feel the team talks are too much of a lottery. For example, if I'm 4-0 up at half time I want the ability to say something similar to "go out there and get more!" rather than declare myself pleased, thrilled, or whatever. There should be more options, but not too many as it could get confusing.
3.) The assistant manager. The assistant needs revamping, I want to leave certain stuff in his hands rather than to do it all myself, isn't that the idea of an assistant after all? I want to delegate stuff to him! Most of all I want to be able to have the assistant give proper team talks, because it's far too common that if I go on holiday (if I've won the league early, for example, and I want to speed the game up a bit) I want him to be able to give more than 'No comment' or whatever it is to the players. I've found they quickly get angry with the assistant for not giving team talks.
4.) More stats please! I'm a statistics junkie, I can't get enough of them. While the game is statistics-based I'd still like to see more in-depth stats.
5.) More board interaction. I'd like to have the ability to talk to the board about stuff like adjusting ticket prices, ask them directly how I'm doing and not just have a screen that says whether they're pleased with my current form or not. I'd also like to be able to discuss sponsorship with them, as well as player behaviour. This stuff might be a bit pointless, but it adds to the immersion in the game.
6.) More interaction with players. I'd like to be able to ask a player about where
they'd like to play, not where I want to play them. If they're concerned with their form I want them to talk to me about it, not just the other way around.
I feel that in the last couple of versions of the game I've felt somewhat detached from the game, it doesn't feel like I'm involved.
It's still an absolutely epic game, and for me it's pretty fast (MacBook with 2GB RAM) so I've got no speed issues. I just want more stats and more interaction really.
All that said, though, I think it's as fun as you're willing to make it. You can choose to be detached from the game if you wish, or you can choose to get heavily involved with everything constantly tinkering with tactics, training, budgets, scouting, etc.