I like them a lot. I own both a 2511t and a 201tcm...I climb with the 2511 about 95% of the time. Bar size is kinda dependent on region and saw mods. Mine's ported, gutted muffler, etc...basically everything you can do to them, so I run a 16" narrow-kerf bar on it. The added bar length allows me to run that saw for longer before I have to switch to a rear handle. The stock chain sucks, I'm a fan of the narrow-kerf 3/8lp chain...another option is 1/4 pitch, but that's the expensive option.
All that being said, the larger 35cc pro-grade top handles have their place...especially if you're doing removals on large hardwoods. Unless you port the 2511, I see it complementing something like the 201 rather than replacing it. Before I ported it, I'd usually climb with the 201 on larger broad trees. Even now that are both ported, the 201 is just a more forgiving saw to run. You can dog it into a log, push on it hard, and not be flirting with stalling out the chain like the 2511.