yeah i've used their free service for years no problem
make sure you use your real email address because they send you warnings about domain deletion to it.
a static ip and domain name are best, but cost, and you can only buy the static from your ISP (as far as i know) however no-ip can link your static or dynamic ip (thier program is mainly aimed at the dynamic IP market) to one of their domain names.
I prefer their free no-ips domain name "yourname.gameserve.com" I used to run a mmorpg from one
DinoHunter (still no nVidia compo voucher!), CPU/GPU Benchmark, DarkFish Encryption DLL, War MMOG (WIP), 3D Model Viewer