Digital pens - any recommendations?

I do, as it happens. My own particular weapon of choice is Livescribe

I type about the same speed I write but, as you say, diagrams and doodles are much easier with a pen.

I'll start with the disadvantages:

You have to use their own paper and notebooks which can be a little expensive but well worth it in my opinion. They do a whole range of notebooks which cover just about everything you should need (I use the Moleskins).  If you have access to a laser printer you can print your own paper for Livescribe, but I reckon it would be cheaper to buy the notebooks. The notebooks also have the added advantage of having a calculator printed on the inside cover, which means you can tap in calculations on the fly and have the results displayed on the pen.

The pen also has a microphone which starts recording when you tap an icon on the bottom of the page. Tap it and keep writing. When you upload the notes to your Livescribe Desktop application (PC or Mac), you'll notice that some of your scrawl is shown on the page in green. Click the mouse over the green bit and your lectures dulcit tones will play out through your speakers. Really useful; you don't miss a thing.  You can run any number of notebooks at the same time, and the pen will keep track of what was written in which book, so they always get loaded up to the right notebook on the Livescribe desktop application.

It can search for words in hand-written notes, just like Evernote and OneNote can, and if that wasn't enough, it has an addon which allows you to OCR your notes into editable RTF files.

Buy it already.

I get about a day and a half's worth of notetaking out of mine.

I'm pretty fast with LaTeX because I don't have to worry about formatting while I'm typing. It all falls apart when I need to get it into Word format though ....

Dr Herbie said:

Digital pens? Pah, in my day we used charcoal on the cave walls ...

You had charcoal??  We had to make our own ink. Out of bed at 4am to milk a squid - those were the days.

The problem is that today's courses are all about team work and collaboration; much harder to get away with your own shorthand.

Good questions. I've found it very reliable. As long as the stroke shows up on the page, then it'll show up on the desktop. Seems to manage to work upside down, but I wouldn't recommend it. It has yet to miss a stroke, unless I forget to switch it on (see later).

It's heftier than a normal pen, but not unbearably so. The biggest problem I find is that I sometimes write a few lines before remembering that I haven't switched it on. I think I'd prefer it switched on when you pressed the pen to the paper.

I often write a note like 'IMPORTANT #1' next to stuff I want to find easily, then I can do a text search and bring it straight to the front.

Oh, it's a good idea  to ask the lecturer/students if it's okay to make voice recordings, especially if you plan to put your notes online.

No problem at all ...

Quick disclaimer: I don't work for these folk and I don't have any shares!

It's not for everybody, but I'm one of those people who backs up his computers religiously, so there's no reason I shouldn't do the same for my handwritten notes.