i'll chime in on this one. i'm an avid DayLite fan and user of about 6 months now. i also use the DayLite Mail Integration (DMI) plugin from them which has proved to be almost as essential as DayLite itself and really fills in the gap between IN and NEXT ACTION. i am a mac consultant doing training, automation, database design, web design and other odds and ends for commercial and residential clients. there is so much in DayLite that it could easily fill a book to discuss it so i'll just hit some basics for how i use it.
i have my contacts and their associated organizations listed as such. incoming email is sent to DayLite in one click via DMI and dealt with accordingly. you can dictate your "next action" right from in Mail, for example...if it is a new contact i will choose "new contact" as the next action and a new entry is made in DayLite with that persons email address and i am brought to their card where i can fill out the rest of their info. all the copy from the email is automatically entered as a note linked to that person. it's a lot more exciting than i am making it sound. if the email was an inquiry about one of my service than i can also tell DMI to go ahead and make a new Opportunity for that person at the same time. this is all from Mail with one click. from the Opportunity stage i will typically assign an Activity Set.
this is where DayLite can really do GTD with some power. Activity Sets are sequential series of events or actions that walk you through a process. they can be linked to people, opportunities, projects, tasks, anything. you should really make an effort to use these as much as you can. some i use are; an activity set that walks me through an initial contact with a potential client, one that walks me through pricing a job, another for stepping through a web design project, the list and possibilities are pretty much endless. i am now trying to make an Activity Set for ANYTHING i do more than once. i figure, once you are familiare with a task why not have the entire process laid out for you and you can just walk through it? this feature is very powerful and flexible. get familiar with it ASAP.
as someone who deals with very little paper i find DMI to be invaluable as a way to track communication with clients. i get a new email and with a single click the body of the message is categorized and linked to the person who sent it and any active project or opportunity they may be linked to. the sales charts are also very cool for giving you a look into the financial future without getting into accounting or money talk. i get extremely motivated when i see a positive forecast, and perhaps even more motivated when it is negative. there is a robust and customizable reporting engine as well. this is one part that needs major work. customizing a report involves tinkering within packages, creating and editing .plist files, and some downright coding. this should simply not be the case. having said that, the ability to mark that final step of a project as "Done" and with a single mouse click upload their finished website and generate an invoice and completion letter to the client along with an envelope and shipping label is quite empowering. speaking of invoicing, i also use Billings from Marketcircle for my invoicing and estimates. it's a new kid on the block but has a gorgeous interface and is just powerful enough for my needs and simple enough to not think about. they really need to integrate these two apps together. DayLite has its timer and billing rates but you can do much with them other than export tab-delimited text.
i suppose i could go on and on but it's quite late. let's keep the DayLite talk going as i'd like to hear from others as well, especially in relation to GTD as i am so new to it and still getting my system in place.
