I've installed it on my SERG and it works as good as the OEM antenna on my bike. Not perfect, but it does the job. The Digital Dakotas are junk. TT is the way to go if you want a hidden antenna that actually works.
No antenna is perfect. The TT is typically mounted in the front of the bike, so if you are driving away from a transmitter it will loose the signal a bit quicker than an external antenna mounted on a tour pack. However, driving toward a transmitter picks up the signal better than the OEM.
If you want the best of both worlds you can use an antenna cable Y (Called Motorola Type) adapter that will let you keep the rear antenna mount connected while also using the TT. You can then remove the rear antenna and use the TT by itself or screw in the OEM antenna/shorty to get max range when traveling in distant locations.
Here's a link to a site that sells the Y for $5.20.
http://www.partsexpress.com/pe/showdetl.cfm?Partnumber=265-584