I played this game quite a bit when it first came out, and I recently restarted trying to get all the badges on Kongregate. I love it! I hate it! I love it! I hate it! I love it! Permanent death is so awesome, and so frustrating.
I did not find the game very repetitive. Having to level up to 20 is a bit boring, but once you have some decent gear (always decide in advance what your next char is going to be, and safe gear for it. You can use everything at level 1) you can quickly and safely level up to 20 in a very short time.
Soloing in godsland is a lot of fun. Dungeons in small groups are a lot of fun too. Doing the major bosses, or minor bosses in large groups, is less fun if you are just starting, because you'll hardly get any loot. I suspect the game will be even more fun with a group of friends, especially with skype, but I haven't so far found such a group yet. I guess I should join a clan someday soon. I would stay away from Onyx or other really end-game content as a new player. You hardly get any loot, and you run a high risk of dying. Working in small groups or solo is, I found, the most fun.
Some classes are definitely better than others. Go wizard, archer or priest if you are relatively new. Archer is very very good early on, but not as good later. Use one to have fun, don't buy the most expensive equipment, don't use stat potions but safe them for your next char, and move on once it dies. Priest is nice because you can heal yourself, but the low dps, especially without the best equipment, makes him bad at getting loot. So go wizard. It's your best bet.
Wizards can keep their distance (which is good), have very high dps and even better huge burst dps. So in godsland for example you can pick one god, burst him with your special, and get loot, without others ninja'ing you. They are a bit squishy, but if you make sure to keep your distance it's ok.
Not that I'm very good myself. I keep dying. Meh ;-( I had such a beautiful wizard, 20 hp and 15 mp above average, and the other stats just above average too. Now he's gone
Guess I'll start again. Got some nice gear in reserve still.