Haven't tried going outdoors yet (and it's raining now! will have to wait for that test!). With my old 5.8ghz vtech I was able to go outside and walk perhaps 30 or 40 ft from the house (down my driveway to the mailbox) before the signal broke up, and from what I'm reading (and from my impression based on in-house performance), I'm guessing this will be comparable if not better. I'll post back after trying this.
Re: UMA - I have an 8300, and never signed up yet for UMA since the signal at home has generally been fine. I may make the change to UMA once a 9xxx for T-Mobile comes out. But I've read up on this, and the router is positioned as an all-in-one replacement to support UMA, normal WiFi requirements (WEP/WPA/WPA2, b/g, etc) and your wired LAN as well as T-Mobile@Home land-line replacement.