I've installed/setup/used several of Racepak's UDX line of dashes both as standalone and with the V300/V500 dataloggers and various sensors. They are easy to read, easy to configure and use, and if you get the "dash-only" UDX they are at a nice price point of about $700 (plus additional sensors.)
http://www.racepak.com/
The MOTEC dash is awesome given the capability for GPS/track overlay capability on the datalog but they are EXPENSIVE (think $6000+ for the entry level dash) and you would want to use one of their ECU's to have a full feature set.
My only beef with the EL-backlit LCD displays is they have a tendency to get washed out and unreadable if you have direct bright sun shining on them (i.e. driving late in the afternoon).
The digital dashes are cool, as are the dataloggers; but you can easily get in over your head and spend a LOT of money. You really need to ask yourself, do you really need acquisition above and beyond what your EFI ECU can give you? If so, then yes an independant datalogging system can be worth it as you can install travel sensors on each corner of the car, driveshaft and wheel speed sensors, therocouples and WBO2 sensors in each header port, record crankcase pressure/vacuum, ride height sensors, etc. When it comes to this area I feel one of the datalogging+ECU integrated solutions (i.e. Motec) is the hot ticket as everything "talks" to each other rather than having an ECU and a datalogging package that function independantly.
Troy