Besides backup, I am responsible for:
 - programming two complex web systems with constant improvements
requirements;
 - help desk support;
 - system administration (network infrastructure, ActiveDirectory,
integrating Linux clients in a Windows networking, etc);
 - proxy, gateway, firewall/security, anti-virus, system update;
 - maintaining a remote server in collocation service (apache/ruby on
rails/log rotation/backup/database/firewall/etc)
 - simple gif creations and all computer related stuff my company needs, as
I am the only computer specialist here...

    

I am in a similar situation and it works out fine. I am a windows
programmer who generates 50K lines of code per year. I am the network
and system administrator for a department of 20 users (and over 15TB
of data) with around 70 machines with mostly windows
desktops/laptops/workstatiosn and linux servers. I build all of the
computers for the network and install all of the software. We have
over 10TB of linux software raid5 and 6 that I have setup and we are
in the process of adding 5TB to 10TB more. I design the everything to
be inexpensive and yet we still have good performance. For us a 3TB
raid 6 server (dual core 4 or 8GB of memory) costs us less than $2000
US for the entire system. The network is complicated by the fact that
we need 2 networks. One for the company/internet the other to archive
gigabit to every single machine. And this is on the cheap also. For
less than $3000 US we have 70 computers connected to 3 X 48 port
gigabit netgear managed gigabit layer 2 switches. The company said
this would cost over 1 hundred thousand if they used the mandated
cisco equipment..
  

Anyways (my point here) the time I spend administering bacula is
probably less than 10 minutes per week so its not like this will take
you a lot of effort.
  

Fortunatelly I am not responsible for implementing the mail server :)

    

I am, well at least the mail server that sends out system messages
when bacula needs a tape or nagios detects a problem with one of the
machines.
  

Not that I am complaing about that (I've already complained to the right
person, but he didn't hire anyone else yet). Actually, I like learning new
things, but the problem is that I'm not that good to reach the expectations
about what I am supposed to do in the desired deadlines.

All this story is to say that I know I won't implement the perfect backup
solution. Mainly because if I think too much in the backup solution, it
seems to others that I am not doing my work, since nobody cares to backup
until there is a disaster, which, fortunatelly, didn't happen yet since I'm
working here (a year and a half past). But at the same time, I don't want to
think what would happen if some important data was lost due to a backup
system failure... When this happen, they will remember I'm responsible for
backup too.

Now, let me explain why it is bad news not beeing able to reclycle the tape
partially:

First of all, we don't have a changer. This means I would need to change the
tapes every day, manually, assuming I will be here all days from monday to
friday.

    

I would not do that since it is way too much work. Have at least 3
tapes and make the recycle period much longer (a month or so). That
way you can do Fulls monthly with incrementals every day and
differentials weekly. I do this for my user (public and private
folder) backups and a DLT-IV drive with a 10 tape rotation. I have
bacula email me of the tape change which probably happens 1 time every
3 weeks and then two times for when the Fulls are run.