Is the elliptical dish for DirecTV the same hardware as the one used for Dish? Could I switch later?

No, the DirecTV elliptical dish is that shape because it accepts signals from two different locations on the horizon. All of Dish Network's regular satellites are in the same location so their dish is only available in the round variety. They do have a satellite that is in a totally different direction. From what I know it carries certain local channels and maybe HDTV (I am not positive on Dish Network satellite locations). Picking up this satellite would require you to use two round dishes.

DirecTiVo series2 is on the horizon (holiday season 2002). However, I would get a series1 box while they're still available and under $100. Don't get the lifetime subscription since the Series2 box will be out by the end of the year and lifetime sub only pays when you keep the equipment over 2 years.

On DirecTV the only HD channels are a couple of the HBO channels and some pay per views. Showtime is not available in HD.

DirecTiVo Series2 should be similar in functionality to the Replay4000. It has 2 USB ports that allow for installation of a NIC and sharing programs between players. There is no word on wether it will support HD signals though.

I have a DirecTiVo on a 46" rear projection HDTV and it doesn't suck, but it's not that good. You see digital artifacts nearly all the time. However, they are not nearly as bad as Comcast digital cable I saw recently.

UltimateTV is no longer. There will be no new hardware coming out from Microshaft as far as I know. Also, the Dishplayer was designed with Microsoft so they are essentially the same thing. The UltimateTV UI is a bit different though.

My current temptation is to spend $200 with AmericanSatellite, getting myself the Phillips/DIrecTiVo unit plus the elliptical dish suitable for future hi-def signals.

This is what I would do.