Since Bluetooth can create all-band interference, is it still worth using?

If you are using Bluetooth to communicate with Cell Phones, you really
don't have that much of a choice. Your only other option would be to
use a wire... If you are considering using Bluetooth for an entire
network of computers I would not suggest using it, but the small
amount of intereference from the Workstation to Device connections
have not caused any problems on my network. I actually get more
interference from the house phones which also operate on the 2.4GHZ
range (as does 802.11b, 802.11g, and Bluetooth).

So what purpose were you looking at using it for?

Bluetooth (typically) transmits at ~0dBm in 1Mhz of an 80Mhz channel
(where the selected 1MHz changes every few mSec).  This is compared to
802.11b/g which uses +20dBm in a 20MHz band of the same 80Mhz channel.

What this means is that wireless LAN ("WiFi") transmits ~100x more
power than bluetooth, and is unlikely to be interfered with by a
bluetooth transmitter.  Additionally, a bluetooth transmitter would
only interfere with ~5% of the transmitted signal -- enough for the
receiver error correction to deal with it.

The only other devices to use the 2.4GHz (bluetooth, 802.11/WiFi) band
are certain cordless phones which also transmit high power relative to
BT.

In short, BT is unlikely to interfere with much of anything, although
other things (WiFi, cordless phones, and uWave ovens) are likely to
interfere with a BT radio.

drm.

Yes it worth using it!
IF you got laptop and u are somewhere and there is no wifi or anythinges else
you can use your phone + bluetooth to use it as modem and surfe the net !
if thats not enough for you , you can use have a wireless headset
i even linked my pc's with bluetooth (sharing internet) + using my
smartphone for that and because its near me (and internet speed was 95
kbs)
and there is few programs thats make your smartphone working as mic ,
webcam and mouse by using bluetooth

:)