Remember that after February 2009, all analog TV broadcasting in the US will end.
The majority of digital broadcasts are in the UHF band (14-49). The higher frequencies mean shorter wavelengths, hence a smaller antenna can do the job.
The antenna element in most small marine
TV antennas is usually a low-gain folded dipole which needs significant amplification to pick out the longer wavelength VHF
The antenna should work fine for local UHF digital broadcasts without the powered pre-amp.
You won't be able to receive digital broadcasts with your old analog NTSC TV
You can get up to two $40 vouchers from the FCC towards the purchase
of a new digital ATSC tuner box which puts out a baseband analog NTSC signal so your old TV will still work - sort of similar to using a cable box.
Your old analog CRT TV consumes more power than a modern LCD digital TV
computer can pull double duty by the addition of an ATSC tuner card and appropriate software
- kill two birds with one stone.
The additional software
can make your PC unstable.
Other countries broadcasting in NTSC won't turn off NTSC for a bit longer.
Most other countries broadcast television using PAL, not NTSC.
I could go on...