Recording music on the PC ...

^ it does have tools for setting up ASIO, and everything works fine. I just can't get latency below 10ms, that's the problem. 

^ yes and no. You can use the GuitarPort as a virtual amp, but only with additional software (called "Gearbox Plug-In". But most people use it as a digital input. You simply plug your guitar into it, and via the Gearbox software (not the plug-in I mentioned above) both processed and unprocessed output of the guitar become available as ASIO inputs.

Of course using the plug-in is really cool because you can record the unprocessed input and always change the amp configuration later. But there are downsides ... you'll need a fast computer, ASIO becomes an issue, and often you need more expensive licenses for the DAW software because the cheaper versions usually only support a limited number of simultaneously running VST instruments and/or audio effects.

^ every soundcard has latency ... it's not a limitation of the GuitarPort as such. The direct monitoring is possible because the software processes the input internally ... it goes from the input through the usb cable to the Line6 driver software, there it gets processed and goes back through the USB cable to the output. The signal never needs to be transferred to another software running on the computer - that's why it's so fast. But if the audio is generated by another VST instrument it needs to be transferred to the Line6 driver, and that's where ASIO comes into play. It's not a big problem for tracks which you play back through the device ... the DAW software compensates for that and simply starts the tracks with a negative offset to compensate for the latency of the interface (and possibly for added latency by software instruments and effects). But obviously this isn't possible for monitoring situations ...

It's difficult to describe ... currently I got the output latency down to 10ms which is something you can work with, but I would fell more comfortable getting it down to 5ms.  

^ thanks - I know about direct monitoring, but when you record drums or keyboards in your DAW application (using software instruments) you can't use direct monitoring anymore, and the latency of the audio output becomes a decisive factor.  

Recently I began to experiment with music recording ... I recorded some tracks almost 10 years ago, but it was a totally different situation back then, there was no USB, no ASIO etc..

Yesterday I installed a demo version of Ableton Live 7 and did some tests with my trusty old Line6 GuitarPort. It turned out that I can't seem to get the ASIO latency below 10ms (buffer size 512, 96khz, 24bit) ... I was wondering whether some of you managed to get a better value.

I also ordered a Line6 KB37 ... an audio interface with integrated midi keyboard. Maybe - since it is much newer than the GuitarPort - I will get better latency with it.

BTW: The cool thing about the Line6 devices is that with their ToneDirect (TM) monitoring you have almost zero latency when recording audio through the Line6 interface inputs, so the latency of the ASIO drivers is no problem there. But as soon as you start recording other instruments - drums, keyboards etc. - the output latency of the device becomes a problem.