(You don't have to do everything in 30 min chunks as you go, you can also manually record other blocks of time spent.)
It's good if you want to set goals for N pomodoros on task area A, M pomos on project B, etc. and then work predominantly in pomo-mode and track your progress on your goals. If you don't use the timer mode, hand-entering time spent probably will get tedious quickly. It's designed to help particularly with time-boxing (i.e. when you're budgeting out a limited amount of time across projects), though I don't use it that way.
I think it's pleasant to use in day-to-day use, decent UI.
Cons: I find that I have a hard time doing my planning (time allocation) on a mobile device screen. I want to do it on a big screen where I can see everything, or on paper. I'm not good at regularly triaging the list and adjusting it, so the goals tend to grow stale and I start ignoring them a bit.