Heres a few tips from me regarding Linux.
Firstly I am making the assumption that you dont have any special requirements other than general usage.
1) Web Browsing - Just like Windows and OSX you have Chrome and Firefox available. Despite the fact that these pieces of software are open source the interfaces are great and are pretty much identical on all three platforms.
2) Office Software - Open Office, and Libre Office are available and for general usage are very capable. These are also free and available on Windows an OSX. The interface is pretty much the same across all three major operating systems. If you absolutely must have MSOffice . you have 3 choices
a) use the online version of office through the browser - your experience will be the same in any browser.
b) use the open source Virtual Box software and use windows & office that way. Virtual Box is a really awesome piece of software!
c) use wine - you wont be able to use the latest and greatest version of office but older versions will work just fine. You might want to consider using codeweavers / crossover office to make installation a breeze. Although distributions such as ubuntu include wine and it is possible to double click "setup.exe" just like in Windows you will probably get a more reliable experience using a wizard (like crossover or playonlinux)
In addition to these options which may be familiar to you there is also Caligra suite - this has a really sumptiuos look and feel!
4) Music Composition - Bitwig Studio (A brand new Ableton Live killer) , Renoise (Octamed Soundstudio on steroids , and then some!) . There are a ton of other interesting music compostion packages out there too . LMMS (like fruity loops), Traktion , EnergyXT , Rosegarden the list goes on.
5) Photo Manipulation - If you want to run photoshop your options are the same as 2) above! Commercial offerings include "Aftershot Pro" , "Pixel" , VueScan. There is also the free GIMP (interface can take time to get used to - there are plenty of online tutorials and is very powerful), Krita plus the multitude of online image editors.
6) 3D modeling - Many of the industry standard 3D modelling software is also available on linux such as Maya , Autodesk , Houdini , Realsoft 3D . There is also the free Blender (previously commercial software) which again has a tricky interface but after following a few of the online tutorials and learning the hot keys you will get to grips with it.
7) Vector editing -(Previously Commercial) Xara Extreme , Inkscape , Karbon14 - there are a ton more but these are the top 3
Watching Video - VLC you are probably already using this on windows or Mac but this software can play pretty much anything you can throw at it! In fact Linux has pretty much the most comprehensive set of tools for playing media than any other platform. from XBMC to Boxee (with home theatre interfaces) .
9) Listening to Music - Again there are many music players for linux ranging from the winamp like "Audacious" , to some really great offerings such as "Banshee" and "Amarok" . There is no iTunes, but lets face it iTunes has a terrible interface and there are much better alternatives on all 3 platforms.
10) Hardware support - While you will probably have more luck installing Ubuntu on a 5 year old PC , than Windows 8 its still a good idea to check hardware compatibility with linux before you purchase a PC or new components. You cant just assume that cheap inkjet from the store will work with linux , just the same as you couldnt make that assumption for OSX or Windows. As a general rule i tend to stick with all intel chipsets as these pretty much work out of the box. If I was building a desktop PC i would almost certainly go for NVidia over AMD for the GPU, although both now provide open source drivers and should work out of the box , the NVidia proprietary drivers are tops!
11) Gaming - No doubt about it this is Linux achillies heel. Windows is still trumps as far as this is concerned. However things are changing - unless you have been hiding somewhere you might already be aware that Valve have recently brought out the Linux based SteamOS , and vowed to port many of their games to Linux. They have really changed the playing field as a result . CryTek announced CRYENGINE is available for Linux and this looks like a trend set to continue.
12) Retro Gaming - UAE , MAME - most of the open source emulators you may already be using started out here so you can continue using them as you see fit!
So - its not all doom and gloom Linux has an exciting ecosystem and while its been a long time coming its gathering momentum as a commercial platform as well as a community one.
