I have a CAT 301.5, probably about 10 years old now. Bought it used, with 600 hours - have well over 1600 on it now between helping building my parents house, stuff around the office, etc.
The 305 is a tad bigger, then the 301.5 so I would imagine some issues I run into with the 301.5, the 305 wouldn't have.
The biggest issue I run into with the 301.5 is weight - it's not heavy enough to really dig into the clay we have, especially when it's dry and hard. Packed gravel (like our truck yard parking lot) is the same thing - 80,000lb semi's running over it all the time tends to make it really hard. The 305, since it has a bit more '***' lets say, probably won't have this issue.
The little machine is strong though, has no issues pushing or lifting - the 305 should be even better. As well, the controls vs. our John Deere ZTS 50 are a lot smoother - the ZTS 50, is a fair bit more used though, with 3400 hours on it.
In my opinion? CAT is about the best mini you can buy - and I've tried them all. If you don't want to pay the price premium for CAT, I would say the John Deere series is the second best for the dollar. Kubota would be up there as well... Bobcat... if you're going to spend the money for a cat, might as well be a true CAT, not a bobcat.